Traditional repair, reconstruction and grafting of soft tissue and vascular tissue require techniques utilizing a reconstructive material or vascular prostheses. For instance, in hernia repair, currently marketed mesh devices generally include a laminated expanded polytetrafluoroethylene (e-PTFE) structure, using e-PTFE laminated to one or more sheets of e-PTFE or to a polypropylene mesh. The rationale for using e-PTFE is to minimize post-operative abdominal adhesions to the mesh. The currently marketed products use e-PTFE on the visceral side (bowel side) and an open pore material such as polypropylene mesh on the fascia or muscular side. The open structured polypropylene material is believed to promote tissue in-growth into the material, thus creating a strong reconstruction.
Postoperative adhesions continue to present significant clinical problems, however, and result in morbidity, mortality, and increased cost. With over 700,000 hernia operations per year, the frequency of secondary procedures to eliminate or otherwise to treat abdominal adhesions is generally in a range of about 50-60%, sometimes higher. No cause for these adhesions is known. While products employing e-PTFE attempt to minimize the incidence of adhesions as a result of the limited porosity and biocompatible nature of the material, the continued high level of adhesion incidence is representative of a clear deficiency in currently marketed technology.
Currently, surgery is the primary option for hernia repair and there are two primary methods of repair: tension repair and tension-free repair. For many years, tension repair was the only method for treating hernias. Tension repair involves incising the abdomen, pushing the protruding tissue back into the abdominal cavity and stitching the incision. It should be noted that while effective, this method causes severe patient discomfort and requires substantial recovery time relative to more modern repair methods.
Tension-free surgery is more commonly used in hernia repair today. It requires less time for recovery vis-à-vis the tension repair method. The tension-free repair method involves incising the abdomen, pushing the protruding tissue back into place and placing a piece of mesh either over or under the defect, which is then sutured into place. The mesh prevents the tissue from protruding through the hole.
Some hernia repair devices use porcine small intestinal submucosa to provide a scaffold for host cells to replace and repair damaged tissue. Once implanted into the hernia defect, host tissue cells and blood vessels colonize the graft and allow for site-specific tissue remodeling. The porcine small intestine tissue is gradually replaced by host tissue. However, the use of animal tissue poses both host immune response tissue rejection problems and potential for transmitted disease from animal to human.
Many types of mesh currently on the market are subject to shrinkage or migration. As a result, use of these products can lead to pain and bowel complications, which in turn may lead to infection.
Vascular repair and requires the use of graft tubing. For instance, abdominal aortic aneurysm repair traditionally requires a large incision in the abdominal wall from just below the sternum to the top of the pubic bone. After the intestines and internal organs of the abdomen are pulled aside, the aorta is clamped and the aneurysm cut open. After removing any damaged tissue, an aortic graft is sewn into the healthy aortic tissue both above and below the weakened area to create a bridge for proper blood flow. Typically, after the graft has been sewn into place, the tissue remaining from the aneurysm sac is loosely sewn over the new graft to prevent the new graft from rubbing against the intestine.
An alternative abdominal aortic aneurysm repair procedure uses an x-ray imaging device to deliver catheter (tube) containing a graft. The catheter is inserted into a blood vessel in the groin and guided to the aorta. Once in the aorta, a balloon at the catheter's tip is inflated and the graft tubing is expanded to a diameter necessary to preclude blood from flowing into the aneurysm. The catheter is removed by deflating the balloon and withdrawing it from the leg. The graft permits the flow of blood through the aorta to the arteries in the pelvis and lower extremities while bypassing the aneurysm.